1. Field of the Invention
The present invention relates to a steering apparatus adapted for use in automotive vehicles, and more particularly to a steering apparatus capable of changing a steering angle ratio of dirigible road wheels relative to a rotation amount of a steering wheel from its neutral position.
2. Description of the Prior Art
In Japanese Patent Early Publication No. 60-209362, there is disclosed a steering apparatus of this kind which includes an input member arranged to be operatively connected to a steering wheel, an output member arranged coaxially with the input member and being integrally formed with an output pinion in mesh with the toothed portion of a rack member for operative connection with a set of dirigible road wheels, an intermediate member interposed between the input and output members and being interconnected with the output member for rotation therewith, and a differential gear mechanism including input and output sun gears different in the number of teeth respectively mounted on the input and intermediate members for rotation therewith and planetary gears different in the number of teeth respectively meshed with the sun gears, the planetary gears being coaxially united and rotatably supported by a common carrier which is rotatably mounted on the input and intermediate members to be driven by an input torque applied thereto from a drive mechanism.
In the steering apparatus described above, the differential gear mechanism is assembled in a position axially spaced from the output pinion. As a result, the axis of the rack member is spaced in a large distance from the lower end of the input member. In such arrangement of the differential gear mechanism, the following problems will be raised when the steering apparatus is mounted to the vehicle body structure.
1) In general, the rack member must be arranged in a limited position to minimize the change of wheel alignment caused by vertical movement of the vehicle suspension. For this reason, the arrangement of the rack member may not be lowered even if a sufficient space is obtained below the input member of the steering apparatus.
2) In general, a steering wheel is mounted on a main shaft which is operatively connected to the input member of the steering apparatus by means of an intermediate shaft and two axially spaced universal joints to eliminate fluctuation of the driver's effort applied to the steering wheel. If the input member of the steering apparatus is raised to arrange the rack member in a desired position, the driver's steering feel will be deteriorated due to fluctuation of his effort.